1. Field of the Invention
The invention relates to a contact probe assembly with fine positioning means.
2. Related Art
Contact probe contactors have been utilized for testing the electrical characteristics of integrated circuits connected to pads on a semiconductor chip. The probe wires of the probe assembly engage the pads to electrically connect the pads in parallel to the test apparatus. Limited force application is needed to prevent damage to the pads or the microelectronic circuit. Additionally, since the pads are located in close proximity, thin deflectable wires functioning as buckling beams must have their contact tips accurately positioned with respect to the pads to prevent shorts between circuits.
European patent application No. 87 104 577.9 describes a contact probe assembly for electrically connecting a test unit to the circular connector pads of a device to be tested. By using a stack of plates, provided with oblong holes, which serve as contact probe guides, this assembly permits employing contact probes of reduced diameter and obtaining, even in view of reduced diameter probes, a low contact resistance between the contact probe and the connector pad of the device to be tested. This is essential for reliable test results.
For reducing the time required for testing devices with regularly recurring patterns of connector pads, it is known to combine several contact probe assemblies in the form of a test head, such as that described in the U.S. Pat. No. 4,686,464 and to use the totality of contact probe assemblies to simultaneously contact the connector pad patterns. This is possible, only, if during the manufacture of the device to be tested, the associated connector pads only differ slightly from the desired dimensions. However, if there are greater differences, such simultaneous contacting of the various patterns by a test head comprising several contact probe assemblies will not yield reliable test results. The contact probes, as a result of thedistortions occurring on the device to be tested during the manufacturing process, either fail to contact their associated pads or they contact pads associated with adjacent probes.
It is the object of the subject invention to solve this problem of aligning the contact probe to the pads by providing a contact probe assembly which yields reliable test results even if several contact probe assemblies are combined to form a single test head and the connector pads do not align exactly to said head.